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    <title>Document</title>
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<body>
    <script type="text/javascript">
        function A() { }
        A.prototype.n = 1
        var b = new A()
        A.prototype = {
            n: 2,
            m: 3,
        }
        var c = new A()
        console.log(b.n, b.m, c.n, c.m)//1 un 2 3

        function Foo() {
            Object.prototype.a = function () {
                console.log('可访问a')
            }
        }
        Function.prototype.b = function () {
            console.log('可访问b')
        }
        var foo = new Foo()
        foo.a();//a
        // foo.b();//err
        Foo.a();//a
        Foo.b();//b

    </script>
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